Novel HIV vaccine strategies: overview and perspective

A human immunodeficiency virus (HIV) vaccine remains a central component in the quest to control the worldwide epidemic. To examine the status of the development of HIV vaccines, we review the results of the efficacy trials carried out to date and the immunologic principles that guided them. Four vaccine concepts have been evaluated in HIV-1 vaccine efficacy trials, and the results of these trials have provided significant information for future vaccine development. While one of these trials demonstrated that a safe and effective HIV vaccine is possible, many questions remain regarding the basis for the observed protection and the most efficient way to stimulate it. Novel HIV vaccine strategies including induction of highly potent broadly neutralizing antibodies, use of novel homologous and heterologous vector systems, and vectored immunoprophylaxis seek to expand and build upon the knowledge gained from these trials.

Characteristics of the gait initiation phase in older adults with diabetic peripheral neuropathy compared to control older adults

BACKGROUND

Gait is deteriorated in older adults with diabetic peripheral neuropathy; however, too little is known about the gait initiation phase. We aimed to determine if gait initiation variables are more sensitive in identifying the extent to which diabetic peripheral neuropathy impacts gait.

METHODS

We examined steps, distance, speed and dynamic balance in the gait initiation phase using a validated algorithm based on wearable sensors in 38 older adults with diabetic peripheral neuropathy and 33 non-diabetic, non-neurologic, non-orthopedic control older adults (≥65 years) under single-task and dual-task gait conditions.

FINDINGS

During the single-task gait condition, the largest differences between the two groups were found in gait initiation steps and dynamic balance (66.7% more steps and 57.2% poorer balance for the diabetic group; effect size = 1.08 and 1.11, respectively; all p < 0.05), while gait speed had a medium effect (10.9% slower for the diabetic group; effect size = 0.54; p < 0.05). Although gait deteriorated for both groups during the dual-task gait condition compared to the single-task gait condition, effect sizes of the between-group differences remained similar. The differences in gait initiation steps and dynamic balance between the two groups were independent of gait speed.

INTERPRETATION

Gait initiation steps and dynamic balance may be more sensitive than gait speed for detecting gait deterioration due to diabetic peripheral neuropathy. Given the association between gait initiation and risk for fall, our findings suggest that gait initiation variables may be important outcomes for clinical management of diabetic peripheral neuropathy.

Estimated lower speed boundary at which the walk ratio constancy is broken in healthy adults

[Purpose] The ratio of step length to cadence (walk ratio) is invariant over a wide range of speeds. However, no studies have investigated details of the change in the walk ratio at slow speeds. It is necessary to explore how walking behavior changes at a low speed to understand the slow walking observed in various conditions such as aging and pathological conditions. In this study, changes in the walk ratio at slow speeds were investigated, and a lower boundary was estimated at which the walk ratio constancy is broken. [Subjects and Methods] Twenty-one healthy adults were instructed to walk along a flat, straight walkway at five different speeds (fast, preferred, slightly slow, slow, and very slow). The walk ratio was calculated from the step length and cadence. [Results] As the walking speed decreased, the walk ratio and variance began to increase abruptly. The initial break in the walk ratio constancy was at approximately 62 m/min. In addition, the boundary of cadence was approximately 98 m/steps/min. [Conclusions] The study successfully determined a lower boundary at which the walk ratio constancy was broken, suggesting that different control strategies are used when walking at less than the gait speed at which constancy is broken in healthy adults. The finding provides valuable information for understanding slow walking observed in individuals with various pathological conditions.

A study of vaccine-induced immune pressure on breakthrough infections in the Phambili phase 2b HIV-1 vaccine efficacy trial

INTRODUCTION

The Merck Adenovirus-5 Gag/Pol/Nef HIV-1 subtype-B vaccine evaluated in predominately subtype B epidemic regions (Step Study), while not preventing infection, exerted vaccine-induced immune pressure on HIV-1 breakthrough infections. Here we investigated if the same vaccine exerted immune pressure when tested in the Phambili Phase 2b study in a subtype C epidemic.

MATERIALS AND METHODS

A sieve analysis, which compares breakthrough viruses from placebo and vaccine arms, was performed on 277 near full-length genomes generated from 23 vaccine and 20 placebo recipients. Vaccine coverage was estimated by computing the percentage of 9-mers that were exact matches to the vaccine insert.

RESULTS

There was significantly greater protein distances from the vaccine immunogen sequence in Gag (p=0.045) and Nef (p=0.021) in viruses infecting vaccine recipients compared to placebo recipients. Twenty-seven putative sites of vaccine-induced pressure were identified (p<0.05) in Gag (n=10), Pol (n=7) and Nef (n=10), although they did not remain significant after adjustment for multiple comparisons. We found the epitope sieve effect in Step was driven by HLA A∗02:01; an allele which was found in low frequency in Phambili participants compared to Step participants. Furthermore, the coverage of the vaccine against subtype C Phambili viruses was 31%, 46% and 14% for Gag, Pol and Nef, respectively, compared to subtype B Step virus coverage of 56%, 61% and 26%, respectively.

DISCUSSION

This study presents evidence of sieve effects in Gag and Nef; however could not confirm effects on specific amino acid sites. We propose that this weaker signal of vaccine immune pressure detected in the Phambili study compared to the Step study may have been influenced by differences in host genetics (HLA allele frequency) and reduced impact of vaccine-induced immune responses due to mismatch between the viral subtype in the vaccine and infecting subtypes.

Altered EMG patterns in diabetic neuropathic and not neuropathic patients during step ascending and descending

Diabetic peripheral neuropathy (DPN) causes motor control alterations during daily life activities. Tripping during walking or stair climbing is the predominant cause of falls in the elderly subjects with DPN and without (NoDPN). Surface Electromyography (sEMG) has been shown to be a valid tool for detecting alterations of motor functions in subjects with DPN. This study aims at investigating the presence of functional alterations in diabetic subjects during stair climbing and at exploring the relationship between altered muscle activation and temporal parameter. Lower limb muscle activities, temporal parameters and speed were evaluated in 50 subjects (10 controls, 20 with DPN, 20 without DPN), while climbing up and down a stair, using sEMG, three-dimentional motion capture and force plates. Magnitude and timing of sEMG linear envelopes peaks were extracted. Level walking was used as reference condition for the comparison with step negotiation. sEMG, speed and temporal parameters revealed significant differences among all groups of patients. Results showed an association between earlier activation of lower limb muscles and reduced speed in subjects with DPN. Speed and temporal parameters significantly correlated with sEMG (p<0.05). The findings of this study are encouraging and could be used to improve rehabilitation programs aiming at reducing falls risk in diabetic subjects.

The Impact on Medical Student Stress in Relation to a Change in USMLE Step 1 Examination Score Reporting to Pass/Fail

The United States Medical Licensing Examination (USMLE) Step 1 was designed to be a benchmark measure of knowledge and has been used heavily in the residency application process. Step 1 has moved from 3-digit scoring to a pass/fail scoring system, in part to decrease the stress associated with the exam. Emerging literature suggests that this transition has led to other stresses for students. Our study compared student stress levels, both overall and in relation to Step 1, leading up to the exam between a scored cohort and pass/fail cohort. We administered to each cohort a 14-item survey that included demographics, the PSS-4 stress scale, and 6 other potential stressors. Data was analyzed using two-tailed t test for independent means and analysis of variance. We found that while there was no difference in general overall stress between the students who took Step 1 for a score and students who took Step 1 pass/fail, we did see differences in stress related to the Step 1 exam. Step 1 stress was significantly lower for the pass/fail cohort than the score cohort during the second year of medical education leading up to the exam. However, this difference in Step 1 stress between the cohorts disappeared by the dedicated study period immediately before the exam. The change in scoring appears to have decreased stress specifically related to Step 1, but this reduction was not sustained as students entered their study period to prepare for Step 1.

PSYCHOMETRIC EVALUATION OF THE HILL ASSESSMENT INDEX (HAI) AND STAIR ASSESSMENT INDEX (SAI) IN HIGH-FUNCTIONING TRANSFEMORAL AMPUTEES

The hill assessment index (HAI) and stair assessment index (SAI) were developed to objectively evaluate ramp and stair gait. This study's purpose was to determine the validity and reliability of these tests in a sample of persons with unilateral transfemoral amputation (TFA) using microprocessor prosthetic knee systems. All subjects were fit with a microprocessor knee system. After accommodation, subjects performed three trials ascending and descending a 5° ramp and a flight of stairs while being recorded on video. Sensitivity and specificity for the HAI was calculated against degree of asymmetry in step length using Dartfish video analysis software. Reliability was assessed using intraclass correlational coefficients calculated using Spearman's Rho (rs). A priori significance level was set at p ≤ 0.05. Twenty (n = 20) individuals with TFA completed the study protocol. Sensitivity and specificity of the HAI were calculated at 88.0% and 75.0% during ascending conditions and 94.0% and 67.0% during descending conditions, respectively. Significant correlations for the HAI included rs = 0.87 and rs = 0.73 within raters uphill and downhill, respectively. Corresponding coefficients of rs = 0.80 and rs = 0.67 were calculated between raters. For the SAI, significant correlations included rs = 1.00 for both comparisons within raters and in the comparison between raters in the ascending condition. A correlation of rs = 0.89 was calculated for the between-rater comparison in the descending condition. The HAI showed moderate to excellent sensitivity and specificity but good to adequate reliability. The SAI showed excellent to good reliability.

Effect of walking surface, late-cueing, physiological characteristics of aging, and gait parameters on turn style preference in healthy, older adults

Turning while walking is a crucial component of locomotion, often performed on irregular surfaces with little planning time. Turns can be difficult for some older adults due to physiological age-related changes. Two different turning strategies have been identified in the literature. During step turns, which are biomechanically stable, the body rotates about the outside limb, while for spin turns, generally performed with closer foot-to-foot distance, the inside limb is the main pivot point. Turning strategy preferences of older adults under challenging conditions remains unclear. The aim of this study was to determine how turning strategy preference in healthy older adults is modulated by surface features, cueing time, physiological characteristics of aging, and gait parameters. Seventeen healthy older adults (71.5 ± 4.2 years) performed 90° turns for two surfaces (flat, uneven) and two cue conditions (pre-planned, late-cue). Gait parameters were identified from kinematic data. Measures of lower-limb strength, balance, and reaction-time were also recorded. Generalized linear (logistic) regression mixed-effects models examined the effect of (1) surface and cuing, (2) physiological characteristics of ageing, and (3) gait parameters on turn strategy preference. Step turns were preferred when the condition was pre-planned (p < 0.001) (model 1) and when the gait parameters of stride regularity and maximum acceleration decreased (p = 0.010 and p = 0.039, respectively) (model 3). Differences in turn strategy selection under dynamic conditions ought to be evaluated in future fall-risk research and rehabilitation utilizing real-world activity monitoring.

Analysis of grain boundary dynamics using event detection and cumulative averaging

To analyze extended time series of high resolution images, we have employed automated frame-by-frame comparisons that are able to detect dynamic changes in the structure of a grain boundary in Au. Using cumulative averaging of images between events allowed high resolution measurements of the atomic relaxation in the interface with sufficient accuracy for comparison with atomistic models. Cumulative averaging was also used to observe the structural rearrangement of atomic columns at a moving step in the grain boundary. The technique of analyzing changing features in high resolution images by averaging between incidents can be used to deconvolute stochastic events that occur at random intervals and on time scales well beyond that accessible to single-shot imaging.

Cross-sectional and longitudinal associations of outdoor walking with overall mental health in later life

PURPOSE

This study aimed to examine the cross-sectional and longitudinal associations of three walking parameters (frequency, duration, and intensity) with overall mental health in older adults.

METHODS

A cross-sectional survey was conducted in 2014 with 1255 community-dwelling older adults aged 65 years and older in Taipei, Taiwan. Among them, 408 participants completed the one-year follow-up survey in 2015. Self-reported outdoor walking during the past 7 days was measured by asking the frequency, duration, and intensity. Metabolic equivalent (MET) values (<2.5, 2.5-<3.5, 3.5-<4.5, and ≥4.5 MET) were assigned to the four levels of speed (slow pace, average, brisk, and fast pace) based on the average walking distance per minute. Overall mental health was assessed using the Five-item Brief Symptom Rating Scale (BSRS-5). Multivariable linear regression models were conducted to explore the cross-sectional and longitudinal associations between outdoor walking and overall mental health, adjusting for socio-demographic factors, lifestyle behaviors, comorbidity and health status.

RESULTS

Among the walking parameters, only walking intensity emerged as a significant predictor of subsequent overall mental health. Multivariable regression analysis showed that light-to-moderate intensity (approximately 2.5-<4.5 METs) was significantly associated with better overall mental health at 12-month follow-up.

CONCLUSIONS

Outdoor walking at light-to-moderate intensity is prospectively associated with better overall mental health in later life.

Reliability and validity of the Chester step test in patients with interstitial lung disease

BACKGROUND

The Chester Step Test (CST) is a simple and inexpensive field test, which requires minimal physical space to assess exercise capacity. Such characteristics make the CST suitable to be used in different settings, however, its measurement properties in patients with interstitial lung diseases (ILD) are unknown.

METHODS

A cross-sectional study was conducted in patients with ILD. First, a CST-1 and a 6-minute walk test (6MWT) were performed. After 48-72 hours, a CST-2 was repeated. A 2nd rater was present in one of the sessions. Relative reliability was measured using intraclass correlation coefficient (ICC1,1 and ICC2,1). Absolute reliability was determined using standard error of measurement (SEM), minimal detectable change at 95% confidence interval (MDC95) and the Bland-Altman method. The values of SEM and MDC95 were also expressed as a percentage of the mean. Construct validity was explored using Spearman correlation coefficient (rs) between the number of steps taken in the best CST and the distance performed in the 6MWT.

RESULTS

Sixty-six patients with ILD (65.5±12.9 years; 48.5%men; FVC 79.4±18.8pp; DLCO 49.0±18.3pp) participated in the study. Relative (ICC 0.95-1.0) and absolute reliability were excellent without evidence of systematic bias. The SEM and MDC95 were 11.8 (14.7%) and 32.6 steps (40.7%), respectively. The correlation between CST and 6MWT was significant, positive, and high (rs=0.85, p=0.001).

CONCLUSION

The CST is a reliable and valid test and might be especially useful to assess exercise capacity in patients with ILD in limited space environments.

Persons with femoroacetabular impingement syndrome exhibit altered pelvifemoral coordination during weightbearing and non-weightbearing tasks

BACKGROUND

Previous studies have reported that persons with femoroacetabular impingement syndrome (FAIS) have diminished posterior tilt of the pelvis during functional tasks. It is not known how this movement impairment impacts pelvifemoral coordination during weightbearing and non-weightbearing movements.

METHODS

Fifteen persons with a diagnosis of FAIS and 15 matched controls performed a deep squat (weightbearing) and a maximum height stepping task (non-weightbearing). Peak hip flexion, posterior pelvis tilt excursion, and the ratio of sagittal plane pelvis to femur motion during the period of pelvis posterior tilt were calculated for each task. Two factor ANOVAs were used to evaluate differences between groups and tasks.

FINDINGS

With regards to peak hip flexion, there were no significant group differences for either task. When averaged across tasks, the FAIS group exhibited significantly less posterior tilt excursion (12.1° (SD 9.1°) vs 20.6° (SD 9.3°)) and smaller pelvifemoral ratios (0.24 (SD 0.14) vs 0.39 (SD 0.16)) compared to the control group.

INTERPRETATION

Persons with FAIS exhibit altered pelvifemoral coordination regardless of weightbearing status. This finding suggests that decreased hip and/or lumbopelvic mobility may contribute to altered movement patterns at the hip.

Is lower peripheral information weighted differently as a function of step number during step climbing?

The importance of peripheral visual information during stair climbing and how peripheral visual information is weighted as a function of step number during step climbing is unclear. Previous authors postulated that the knowledge of predictable characteristics of the steps may decrease reliance on foveal vision and transfer the online visual guidance of stair climbing to peripheral vision. Hence the aim of this study was to investigate if and how the occlusion of the lower peripheral visual field influenced stair climbing and if peripheral visual information was weighted differently between steps. Ten young adult male participants ascended a 5-step staircase under 2 visual conditions: full vision (FV) and lower visual occlusion (LO). Kinematic data (100Hz) were collected. The effect of Vision and Step condition on vertical forefoot clearance was examined with a Repeated Measures 2-way ANOVA. Tukey's HSD test was used for post-hoc comparisons. A significant interaction Vision x Step and main effect of Step were found (p<=0.04): vertical forefoot clearance was greater in LO compared to FV condition only on the 1st and the 2nd steps (p<0.013) and on the last step compared to the other steps (p<0.01). These findings suggest that online peripheral visual information is more relevant when negotiating the first two steps, rather than the end of a staircase and that the steps subsequent the first few ones may require different information likely based on proprioception or working memory of the step height.

New taxonomy for assessing manual material handlers' footstep patterns

Current taxonomies for assessing foot strategies in manual material handling lack exhaustive classification of foot movements and foot positioning. They also fail to consider different instants of the task as checkpoints to relate foot strategies. The goal of the study was first to develop a new taxonomy to assess foot positions and motions considering those limitations. The second goal was to assess reliability and reproducibility using raw agreement percentages, Cohen's kappa, prevalence-adjusted, bias-adjusted kappa and Gwet's AC1. A filmed task consisted of transferring boxes from one pallet to another. Intra- and inter-rater reliability were assessed reviewing 23% and 10%, respectively, of video data. Reproducibility and reliability results are substantial and almost perfect on average. In comparison to similar studies, reproducibility and reliability were considered acceptable.

Hot and cold inhibitory control in bipolar disorder: An antisaccade study of emotion processing and attentional modulation

BACKGROUND

Bipolar disorder (BD) is associated with inhibitory control impairments, but traditional inhibitory control tasks may be confounded by reading ability, which is impaired in some BD patients. Eye-movement tasks assessing antisaccade performance avoid these limitations, but few studies have examined inhibitory control in BD using such tasks, particularly those modulating valence and attention.

METHOD

We used eye-tracking in a sample of 44 euthymic BD patients and 30 controls to measure antisaccade performance on tasks employing emotional "hot" and nonemotional "cold" stimuli. Attentional modulation was examined by comparing performance across step and gap trials.

RESULTS

No significant between-group differences were found in antisaccade error rates or latencies for neutral or emotional stimuli. Both groups performed worse during neutral compared to emotional stimuli. BD patients showed a slight negativity bias, trending toward slower responses to negative compared to positive stimuli. Both groups performed more quickly and accurately during gap compared to step condition.

CONCLUSIONS

These findings suggest that inhibitory control in BD, as measured by antisaccade performance, is influenced by valence and attentional modulation in a similar way to controls. The lack of significant group differences contrasts with previous research, necessitating further investigation into the mechanisms of antisaccade performance in BD.

A randomized controlled trial of an app-based intervention on physical activity and glycemic control in people with type 2 diabetes

BACKGROUND

We investigated the effects of a physical activity encouragement intervention based on a smartphone personal health record (PHR) application (app) on step count increases, glycemic control, and body weight in patients with type 2 diabetes (T2D).

METHODS

In this 12-week, single-center, randomized controlled, 12-week extension study, patients with T2D who were overweight or obese were randomized using ratio 1:2 to a group using a smartphone PHR app (control group) or group using the app and received individualized motivational text messages (intervention group) for 12 weeks. During the extension period, the sending of the encouraging text messages to the intervention group was discontinued. The primary outcome was a change in daily step count after 12 weeks and analyzed by independent t-test. The secondary outcomes included HbA1c, fasting glucose, and body weight analyzed by paired or independent t-test.

RESULTS

Of 200 participants, 62 (93.9%) and 118 (88.1%) in the control and intervention group, respectively, completed the 12-week main study. The change in daily step count from baseline to week 12 was not significantly different between the two groups (P = 0.365). Among participants with baseline step counts < 7,500 steps per day, the change in the mean daily step count at week 12 in the intervention group (1,319 ± 3,020) was significantly larger than that in control group (-139 ± 2,309) (P = 0.009). At week 12, HbA1c in the intervention group (6.7 ± 0.5%) was significantly lower than that in control group (6.9 ± 0.6%, P = 0.041) and at week 24, changes in HbA1c from baseline were significant in both groups but, comparable between groups. Decrease in HbA1c from baseline to week 12 of intervention group was greater in participants with baseline HbA1c ≥ 7.5% (-0.81 ± 0.84%) compared with those with baseline HbA1c < 7.5% (-0.22 ± 0.39%) (P for interaction = 0.014). A significant reduction in body weight from baseline to week 24 was observed in both groups without significant between-group differences (P = 0.370).

CONCLUSIONS

App-based individualized motivational intervention for physical activity did not increase daily step count from baseline to week 12, and the changes in HbA1c levels from baseline to week 12 were comparable.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03407222).

Standard versus low-dose computed tomography for assessment of acetabular fracture reduction using novel step and gap measurement technique

PURPOSE

Quality of reduction is of paramount importance after acetabular fracture and is best assessed on computed tomography (CT). A recently proposed measurement technique for assessment of step and gap displacement is reproducible but has not been validated. The purpose of this study is to validate a well-established measurement technique against known displacements and to determine if it can be used with low dose CT.

METHODS

Posterior wall acetabular fractures were created in 8 cadaveric hips and fixed at known step and gap displacements. CT was performed at multiple radiation doses for each hip. Four surgeons measured step and gap displacement for each hip at all doses, and the measurements were compared to known values.

RESULTS

There were no significant differences in measurements across surgeons, and all measurements were found to have positive agreement. Measurement error < 1.5 mm was present in 58% of gap measurements and 46% of step measurements. Only for step measurements at a dose of 120 kVp did we observe a statistically significant measurement error. There was a significant difference in step measurements made by those with greater and those with fewer years in practice.

CONCLUSION

Our study suggests this technique is valid and accurate across all doses. This is important as it may reduce the amount of radiation exposure for patients with acetabular fractures.

Park proximity and all-day and time-specific physical activity and sedentary behaviour in older adults

BACKGROUND

Proximity to parks has been suggested as a factor influencing physical activity in older adults. However, it remains unclear the optimal distance between residences and parks for promoting physical activity and reducing sedentary time and whether these associations vary by the time of day. We examined whether the proximity to neighbourhood parks at varying distances is associated with all-day and time-specific physical activity and sedentary behaviour in older adults.

METHODS

Data were collected from 214 older adults receiving hospital services in Taipei, Taiwan. The number of parks within 400m, 800m, and 1,600m of participants' residences. Physical activity and sedentary behaviour, stratified by time of day (morning, afternoon, and evening), were measured using accelerometers. Adjusted linear regression models were used to estimate associations of park proximity with activity and sedentary outcomes.

RESULTS

Parks located within 400m and 800m of participants' residences were more markedly associated with longer time in physical activity and less sedentary time compared to parks located 1,600m away. A greater number of parks within 400m and 800m was positively associated with walking steps and light-intensity physical activity while both distances were negatively associated with sedentary time. The associations between park proximity and behavioural outcomes were mainly attributable to that during the afternoon and evening.

CONCLUSIONS

Our findings suggest that favourable access to parks within 800m of older adults' residences is associated with more physical activity and less sedentary time, particularly during the afternoon and evening. Future longitudinal studies are required to corroborate these associations.

The impact of neck pain on gait health: a systematic review and meta-analysis

BACKGROUND

Evidence exists demonstrating the negative impacts of chronic musculoskeletal pain on key measures of gait. Despite neck pain being the second most common musculoskeletal pain condition, there is a paucity of evidence exploring the impacts of neck pain specifically on these outcomes. The aims of this work were to systematically review the current evidence of the associations between chronic neck pain and measures of gait health and to conduct meta-analysis for quantitative assessment of the effect sizes under different walking conditions.

METHODS

Systematic review was conducted following PRISMA guidelines. Databases searched included MEDLINE, Embase, Web of Science, CINAHL, and PEDro. Eligible study designs included observational studies consisting of an exposure group with chronic neck pain and control group without chronic neck pain and primary outcomes relating to gait health. For outcomes amenable to meta-analysis, a random-effects model was used to derive summary estimates of Hedge's g depicted graphically with forest plots. Other gait outcomes were narratively summarized. Risk of bias was also assessed.

RESULTS

The original search yielded 1918 articles; 12 met final eligibility criteria including 10 cross-sectional studies. Outcomes were grouped first by the five domains of gait: pace, rhythm, asymmetry, variability, and postural control; and second by the tested walking conditions. Meta-analyses for gait speed revealed large effect-sizes indicating that individuals with chronic neck pain had slower measures of gait and lower measures of cadence. Gait outcomes that were narratively summarized supported these findings.

CONCLUSION

The quantitative and qualitative findings of this systematic review and meta-analysis suggest a negative impact of CNNP on measures of gait health, particularly gait speed, under various walking conditions. However, broad interpretation of these results should be cautious. Testing gait under dual task conditions may be particularly sensitive to the impact of CNNP, and future work is needed to better understand how pain disrupts this important functionality of the locomotor system. Additionally, consideration should be made to assess measures of variability and investigate these relationships in the older adult population.

A novel breath pattern model and analysis to minimize patient discomfort in medical ventilators

Typical waveforms used for the simulation of pressure and volume-controlled ventilation in medical ventilators have been extensively studied in the literature. The majority of simulation studies reported employ the step pattern or ramp pattern to model the pressure and flow variations in pressure/volume-controlled ventilation. It was observed that the above waveforms tend to add to the discomfort level of patients due to the presence of jerks in derivatives of pressure/flow variations; the pressure/flow variation of air and oxygen mixture should be smooth so that the patient discomfort is kept at a minimal level. To overcome the above-mentioned drawback, a careful study of the flow/pressure simulation using a cycloidal pattern during the inhalation and exhalation phases of the breath cycle was proposed and investigated in this work. Based on transient analysis of the pressure variation simulation, it was observed that the air and oxygen mixture delivered to the patient was relatively jerk-free due to the finite values of first and second-order derivatives of pressure/flow curves. Mathematical models of the proposed simulation study of the cycloidal pattern of flow variation in both pressure/volume-controlled ventilation, are formulated and presented for use by ventilator designers. A comparative study of the simulation of step, ramp and cycloidal profiles applied to the breath cycle in a typical pressure-controlled ventilation is carried out and a marginal decrease in tidal volumes was observed in the case of cycloidal profiles for a given set of ventilator settings and the results are discussed. A typical natural breath pattern of a healthy adult was experimentally measured using a CITRIX breath analyser and the above mathematical model for the volume-controlled ventilation was found to closely describe the natural breathing process, using statistical parameters. Thus, the proposed cycloidal profile of pressure/flow variations in medical ventilators will be a better alternative, when compared to the step/ramp profiles investigated in this work; further, the proposed cycloidal profile matches closely with the natural breath pattern, based on typical experimental studies.